Project Summary Exosomes have been reported as biomarkers of disease and drug response. They are transport vesicles that are secreted from cells and deliver microRNAs, mRNA, and proteins to other cells; they can transport mole- cules to other local tissues, or to distant tissues through blood circulation. Both the exosomes and the target cells contain some surface molecules (e.g. lectin proteins) that appear to impact the rate (kinetics) and site of exosome uptake. These delivery instructions are changed by the effects of disease or drug treatment and re- sult in altered exosome uptake. Thus, understanding these changes may elucidate new biomarkers that are associated with both diseases and drug responses. Collectively, these data indicate that critical unknowns are 1) what factors alter exosome kinetics and 2) how do those factors alter the delivery instructions. In this project, I will focus on understanding how alterations to the secreting cells alter the kinetics of the secreted exosomes. The applicant's long-term goal is to improve the rational use of exosomal biomarkers to predict disease and treatment response. Understanding the exosome kinetics would help to optimize exosomal-biomarker valida- tion study designs and may lead to studies that elucidate the mechanisms underlying biomarker associations. The central hypothesis is that secreted exosomes from different cell types have different exosome kinetics and that the drug treatment of diseased and normal cells changes the kinetics of the secreted exosomes. Aim 1 will determine the in vivo exosome kinetics of exosomes secreted by different cell types. Aim 2 will determine the in vivo kinetic parameters of exosomes derived from drug treated cells. By completion of these studies, the ap- plicant expects to develop kinetic models that discern kinetic parameters of exosomes in blood. This K08 Men- tored Clinical Scientist Research Career Development Award details a 4-year training plan designed to accom- plish 4 main objectives: (1) learn the techniques and concepts required to conduct in vivo exosome kinetic studies and advance the field of clinical pharmacology, (2) train in the concepts and application of advanced bioinformatics and data processing of exosome kinetic parameters to advance the field of clinical pharmacolo- gy, (3) gain experience translating basic findings into collaborations, and (4) develop professional skills neces- sary for a successful and independent academic career. The Indiana University School of Medicine (IUSM) has made a commitment to promoting the growth of health research through the training of young investigators. The Division of Clinical Pharmacology is well-funded, highly collaborative, with strong research projects in adult, pediatric, and obstetric pharmacogenetics, drug metabolism, and drug interactions. The applicant's train- ing will include mentors and a faculty advisory committee consisting of NIH-funded investigators with expertise in kinetics, bioinformatics, physiologically-based computational modeling, and circulating exosome biology. By the completion of this K08 award, I will develop high-quality publications, fruitful collaborations, independent (R01) and collaborative research funding with feedback from my mentors and faculty advisors.